MALONDIALDEHYDE FORMATION IN LIVER MITOCHONDRIAL AND MICROSOMAL FRACTIONS OF VITAMIN-E-DEFICIENT AND SELENIUM-DEFICIENT RATS AS A FUNCTION OF ALPHA-TOCOPHEROL LEVEL - THE EFFECT OF TREATMENT IN-VITRO WITH IRON

Weanling rats were given diets with adequate vitamin E and selenium or deprived of one or the other or both, nutrients. After 28 days, liver mitochondrial and microsomal fractions were prepared and alpha-tocoph erol (alpha-T) and selenium measured. Alpha-tocopherol fell by eight-f old in the doubly deficient rats and selenium fell three-fold. Malondi aldehyde (MDA) was found to be undetectable by a sensitive HPLC method . The fractions were subjected to peroxidative stress in in vitro usin g 0.5 mM Fe2+/10 mM ADP, and MDA and alpha-T were measured at interval s during 30 min. The results showed that in the mitochondrial fraction s there was a lag time of at least 2 min before peroxidation became si gnificant, during which time most of the alpha-T was consumed. In the microsomal fraction the lag phase was very short prior to the establis hment of a linear rate of peroxidation, although little alpha-T was us ed up. It was concluded that the mitochondrial fraction withstood the peroxidative challenge better than the microsomal fraction even though the initial level of alpha-T in the microsomal fraction was about dou ble that in the mitochondrial fraction. Selenium deficiency had no eff ect on the length of the lag phase of the fractions which therefore ap pears to be a characteristic of mitochondrial or microsomal fractions.